modern research physics

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Citrus fruits are tropical and sub-tropical crops. The main problem in sub-tropical area is chilling and frost damage. Regarding the sensitivity of citrus fruit to low temperature and the conjunction of the fruit harvest season with low temperature, the investigation of the physiological impacts of low temperature treatments are very important. In this study, flavedo tissue of five cultivars of citrus fruit was examined to compare some enzymatic antioxidants activities including Superoxide dismutase (SOD), Ascorbate peroxidase (APX), peroxidase (POD) and Catalase (CAT) under various cold treatments, i.e. control (~15), 3, 0, -3 and -6 ^°C in two stages of before and after ripening of the fruits. The high activity of SOD enzyme in the flavedo tissue of the examined cultivars indicated that this tissue is the first defensive line of the fruits facing low temperatures treatments. The activity of CAT enzyme in the flavedo tissue of Sanguinello before and after ripening stages was higher in all low temperature treatments compared with other cultivars. Unshiu and Local Orange had maximum and minimum activity of APX enzyme, respectively in both stages. Also, Unshiu, Sanguinello and Local lemon showed increasing activity of POD enzyme by decreasing temperature

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In the present study, the effects of indole acetic acid (IAA) on certain physiological and biochemical parameters in Glycine max (L.) Merr under aluminum chloride (AlCl₃)stress were studied. Seeds were sterilized and cultured in petri-dishes. Six days old seedlings were transferred to pots, and then they were irrigated with Hoagland solution in a growth chamber (with 16 h light period per 24 h, with day / night temperatures of 25/18 ºC respectively). Twenty days old plants were treated with different concentrations of AlCl₃ (0, 50, 100, 200 and 300 µM) and IAA (0, 50 and 100 µM). Plants were harvested 15 days after treatment. The plants exhibited decline in the relative water content (RWC), protein, soluble sugars, the chlorophylls a and b, carotenoids contents and photosynthetic rate with increase of aluminum chloride concentration, but the respiration rate and CO₂ compensation concentration were increased. With addition of IAA to culture solutions containing aluminum, the plants showed further decrease in the amount of soluble sugars, chlorophylls a and b, carotenoids and photosynthetic rate and further increase in other parameters. With increasing of aluminum concentration to culture solutions with and without IAA unsoluble sugars, proline and lipid peroxidation increased.
 

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Vegetation of Kasf forest with an area of over 12 ha, located in the east-west direction at a distance of 20 kilometers north of the city of Bardaskan, between 57° and 52' and 30" to 58° and 00' and 00" East longitude and 35° and 22' and 30" to 35° and 30' and 00" North latitude, in a mountainous arid region with a minimum and maximum temperature of -10 and +45° C , respectively and average annual precipitation of 155 mm, at an altitude of about 1600 m above sea level with 15% slope was studied using floristic method 2 years after fire and life forms and geographical distribution of plant species were determined. Sixty nine plant species belonging to 29 families (25 Dicots, 3 monocots and one gymnosperm). The largest families were the mint (Lamiaceae) with 11, Compositeae (Asteraceae) with 9 and carnation family (Caryophyllaceae) with 5 species. The life forms included Therophytes with 36% (25 species), Hemicryptophytes 29% (20 species), Chamaephytes 16% (11 species), Phanerophytes 13% (9 species) and cryptophytes with 6% (4 species). The high percentage of Hemicryptophytes indicated dominance of cold mountainous climate and the presence of Asteraceae species such as harmala (Peganum harmala) showed sever disturbance had taken place in the region and thus, the need for administering greater ecological care and employing more extensive environmental supervision and management was identified.

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Microbial analysis of ground water, as a solely supplying water sources must be evaluated in many areas. Because of the treatment of water always cannot remove all pathogenic bacteria which are leaked from domestic wastewater, bacterial survey of Bojnourd groundwater sources were carried out in this study. For this reason, membrane filter (MF) technique and Most Probably Number (MPN) methods were used to evaluate the quality of the water. Escherichia coli (E. coli) and Enteroccocus faecalis (E. faecalis) were traced as excremental indices. E. coli was detected from three out of six stations and E. faecalis was only isolated from one of stations. Although molecular techniques are very rapid and exact technique for detection of microbial community and are able to identify Viable But Not Cultivable bacteria (VBNC) but are unable to distinct live and dead microorganisms. By using standard technique it is possible to study live microorganisms. It can be concluded that both E.coli and E.feacalis was detected in some stations. The sanitization of groundwater must be revised to less the microbial population in this groundwater.